With the ongoing standardisation of 3GPP long term evolution (LTE or E-UTRAN) and WiMAX (IEEE802.16) air interfaces, in addition to existing standards (GSM/GPRS and UMTS) an increasing diversity of radio access technologies (RATs) will be present in the future, Operators will require sophisticated mobility mechanisms to simultaneously steer users to appropriate RATs while also spreading the load across the different technologies.
In today's wireless systems like GSM/GPRS or UMTS, typically UE-controlled cell reselection algorithms currently operate independently of any subscriber-specific or service considerations [for UMTS e.g. in 3GPP TS 25.304]. All UEs are handled in the same way based on parameters broadcast on the BCCH [for UMTS e.g. in 3GPP TS 25.331], and hence follow the same cell reselection strategies. Similar as for the idle mode the decision criteria for both mobility related and radio resource related decisions are independent from any subscriber or user type information. So in general the decisions are based on terminal capabilities and to some extent on current service usage or specific information provided by the core network (CN) during the service establishment (e.g so-called “service based handover” which gives an indication from the CN to the RAN that a certain bearer might be handed over to a specific RAT or not). This all relates to the demand of providing similar service equally for all users of the mobile system.
With the advent of a demand for increased data rates and the cost reduction implied by specific tariffs of the mobile operators, an increasing demand is foreseen for user as well as service differentiation, for example in mobility decisions. Qualifying data by means of Quality of Service (QoS) can provide some means to differentiate the subscribers but mobility related decisions (especially while being in idle mode) can't reliably be taken based on this kind of information designed for differentiating traffic of different services using prioritised packet delivery rather than independent tailored to control mobility based upon the type of user.
3GPP has already specified access control classes to restrict access to mobile networks to a set of subscribers belonging to a set of access control classes during severe network congestion. It is proposed that a similar kind of user differentiation is available within the RAN for mobility decisions so that users can be spread appropriately across RATs.
In addition to load distribution across RATs, similar mechanisms may also be required to distribute load across different carriers of different bandwidths on the same RAT.
EP 1 519 607 A1 discloses a method and apparatus for performing radio resource management, wherein the method allows a radio access network to selectively influence the mobility decisions as well as the radio resource control decisions for a specific terminal based on information received from a core network entity.
US 2002/0193139 A1 discloses a method for network/cell/interface selection in mixed networks, wherein a mobile terminal can select different modes of operation, each corresponding to one of a plurality of core networks. The selection is based on selection parameters furnished to the mobile terminal by broadcasting system information or packet system information in the radio cell.